When vim mode is enabled, previously if Cmd-F (or platform equivalent)
was pressed, enter will go to the editor's first match, and then hitting
enter again goes to the next line rather than next match. This PR
changes it to make enter go to the next match, which matches the
convention in most other programs. The behavior when search is initiated
with / is left unchanged.

This is a reopen of #35157, rebased and fixed.
Closes #7692

Release Notes:

- In vim mode, when search is triggered by the non-vim mode shortcut
(cmd-f by default) enter will now behave as it does outside of vim mode.

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Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>